Whether you spell it grey or gray, here's a good rule of thumb to keep in mind when you encounter one of the issues above: Something is not right. Not to oversimplify, but if you are able to perform some functions in L2L, say on one line or machine, but not in another line, machine, schedule, user record, etc., look at the setup of the working item vs. how the non-working item is set up.
This is almost certainly the case, whether you're talking about Line Cycle Times, Shifts, templates, scheduled reports, thresholds, etc. If it can be set up in L2L, something can inadvertently be set up differently. I would estimate that 97% of the time, when we hear that something isn't working correctly, an expected radio button "Won't let me click on it", "The hyperlink doesn't take me anywhere.", "My selection is greyed out.", that tells us that something in the setup isn't right.
Especially when immediately followed by, "This is the only line where this is happening." or, "I can see this and do this everywhere else. It's just this one _ _ _ _ _."
It can take a minute to find the discrepancy in the setup. It takes a little bit of digging and a little bit of comparing. Here's what we do and how you can diagnose the problem more quickly: Open the details pages of the items you wish to compare. If at all possible, utilize an extra monitor or two, so you can compare the screens side by side. If you don't have an extra monitor at your disposal, try capturing a screenshot or snippet of one page, and display that next to the other page. Be sure you're using a known good (i.e., working correctly) setup alongside the problem child.
You will encounter this on all websites and all applications, so don't let your frustration get the better of you. Just take a few minutes and try the suggestions above. You'll probably find it faster than you thought. And this is the best way to ingrain the lesson. When you find it, be sure to share it with your teammates. That will further reinforce the learning experience!